Added ability to add people to tags when viewing the tag details page

[cabal95]

Contributor Agreement

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Context

What is the problem you encountered that lead to you creating this pull request?

Inability to add people directly to a tag without going to their profile page. See #556.

Goal

What will this pull request achieve and how will this fix the problem?

Grant ability to do so.

Strategy

How have you implemented your solution?

When viewing the members of a tag, if the tag entity type is a Person then the Add button becomes available in the action bar. Upon clicking a modal dialog opens with the person picker expanded by default and ready to type in a person's name. You can then either Save and it will close the modal or Save And Add and it will add the person and then re-open the drop down for typing another name.

Tests

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Possible Implications

What could this change potentially impact? Are there any security considerations? Where could this potentially affect backwards compatibility?

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Documentation

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